1. Technical Field
The present invention generally relates to a method and apparatus for writing a grating; and more particularly to a method and apparatus for writing a grating in a large diameter optical waveguide (also known hereinafter as “cane” or “cane element”).
2. Description of Related Art
If any collocated grating is written beyond the end of the uniform strain region in either or both ends of the ground region of the element, the grating(s) will chirp under compression. However, the longest possible grating is desired for the filter shape properties. For this reason, the placement tolerance of the grating has been reduced to the smallest possible value.